Insects. 5175 



A most valuable means of diagnosis, used by Fermaire in establish- 

 ing sections, is afforded by small longitudinal furrows (" sillons"), one 

 on each side of the thorax at the base, but they often require some 

 tact to observe them, and should be exposed to an oblique light. In 

 some species, as in lineatocollis, they are very large and curved, in 

 others they are reduced to a somewhat obscure depression, but are 

 constant. 



The colour of this genus varies much with the degree of maturity ; 

 but the true cinereous or ferruginous tinge which characterizes certain 

 species may always be recognised by a little attention, even in the 

 most immature condition. 



Haliplus, Latr. 



1. H. elevatus, Panz. This species requires no remarks. It is not 

 to be mistaken, from its size, elevated lines, the elytra, &c. It is 

 abundant from spring to winter in streams at Cowley; also in the 

 Ravensbourne near Sydenham, and the brooks running into it, &c. &c. 



2. H. mucronatus, Steph. 



3. H. fulvus, Fab. 



4. H. flavicollis, Sturm. 



5. H. variegatus, Sturm. 



These four species are nearly allied. They may be distinguished 

 from those which follow by their large size ; and especially from con- 

 finis, lineatocollis, ruficollis and fluviatilis, by the absence of furrows. 



First, mucronatus at first sight, in colour, &c, resembles fulvus, 

 but is longer, narrower and more parallel, and has no black lines on 

 the punctate striae. There is a remarkable prolongation of the apices 

 of the elytra internally, but the most prominent difference is in the 

 thorax, which is not so much narrowed in front ; posteriorly its sides 

 are nearly parallel, anteriorly they turn a little inwards ; whilst in ful- 

 vus, and also flavicollis, they form right lines, inclining forwards. 

 Rare. I have taken it only near Cambridge, at Swaffham Prior, and 

 Hornsea Fen. 



Secondly, flavicollis is distinguished from fulvus by its paler immacu- 

 late elytra, and by the absence of the ferruginous tint manifest in 

 fulvus, even when immature. It is rather smaller and more attenuated 

 behind : fulvus has, I believe always, more or less numerous black 

 longitudinal lines on the elytra, sometimes more or less confluent. 

 Both are very common, but flavicollis occurs generally in large pieces 

 of water, such as canals. I have seldom, if ever, taken it in small 

 pits. 



